Windmill



FIG. 1 is a front view of a windmill in accordance with the present design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a rear side view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a perspective view thereof. 

The ornamental design for a windmill, as shown. 